1. Field of the Invention
The present invention relates to a variable capacity swash plate type compressor adapted for use in an air conditioner for a vehicle, and more particularly to such compressor of an improved type which has a hinge mechanism for pivotally supporting a swash plate.
2. Description of the Related Art
In automotive air conditioners, a variable capacity swash plate type compressor is widely used, which generally comprises a drive shaft, a rotor or lug plate mounted on and rotating with the drive shaft, and a swash plate. The swash plate is rotatably disposed on a spherical outer surface of a spherical sleeve member slidably mounted on the drive shaft.
Between the rotor and the swash plate is arranged a hinge mechanism which normally includes a first arm member projecting from the rotor in the rear direction of the compressor, a second arm member projecting from the swash plate in the front direction of the compressor, and a pin member connecting the first and second arm members through a pair of holes each formed in the respective arm members. One of the holes, for example the hole formed in the rotor is elongated to guide the pin therein according to the change of inclination angle of the swash plate. The sliding motion of the pin within the elongated hole changes the inclination angle of the swash plate. The sliding motion of the pin within the elongated hole changes the inclination angle of the swash plate. The compressor also includes a plurality of pistons each engaged with the swash plate via semi-spherical shoes.
The hinge mechanism allows the swash plate to slide along and change its inclination angle with respect to the drive shaft. The hinge mechanism also allows the swash plate to rotate together with the drive shaft and the rotor. Rotation of the drive shaft causes the rotor and swash plate to rotate therewith, and accordingly, each pistion engaged with the swash plate reciprocates within respective cylinder bores so that suction and compression of the refrigerant gas are completed. The capacity of the compressor is controlled by changing the inclination angle of the swash plate according to the pressure difference between the pressure in the crank chamber and the suction pressure.
In the above described variable capacity swash plate type compressor, the swash plate rotates with the drive shaft and nutates back and forth with respect to the rotor, and the rotation of the swash plate is converted into the reciprocation of the pistons within the respective cylinder bores. A suction force acts on the swash plate from the pistons during the suction stroke while a compression reaction force also acts on the swash plate from the pistons during the compression stroke. Therefore, the swash plate is subject to a twisting motion or bending moment due to the suction and compression reaction forces acting from each piston on the swash plate. Moreover, since a torque exerted by the drive shaft is transmitted to the swash plate through the hinge mechanism, the swash plate is twisted with respect to the rotor in a direction different from the back and forth nutating motion.
As a solution for the above mentioned problems, U.S. Pat. No. 5,540,559 discloses a variable capacity compressor having an improved hinge unit. The hinge units comprise a pair of brackets protruding from the back surface of the rotary swash plate, a pair of guide pins each having one end fixed to each bracket and the other end fixed to a spherical element, and a pair of support arms protruding from the upper front surface of the rotor. Each support arm is provided with a circular guide hole into which the spherical element of the guide pin is rotatably and slidably inserted. U.S. Pat. No. 5,336,056 discloses a hinge means including two support arms extended axially rewardly from the rotary support. Each of the support arms has a through-bore in which a race member is fixedly seated to tunably receive a ball element. Each ball element, too, has formed therein a through-hole operative as a guide hole permitting an axial slide of a guide pin therin. The guide pins are fixedly press-fitted in two through-bores formed in the rotary drive element of the swash plate assembly, respectiverly.
However, the hinge mechanisms disclosed in the above U.S. Patents are complex, and in particular, they require precise and time-consuming machining to form the circular guide holes and spherical elements of the guide pins in U.S. Pat. No. 5,540,559 and to form through-bores in U.S. Pat. No. 5,336,056. Moreover, to make symmetrical the hinge mechanism including two support arms protruding from the rotor or the rotary drive element must be accurate and therefore is relatively burdensome. These raise the cost in manufacturing the compressor. Therefore, it is advantageous to provide a compressor with a hinge mechanism which is simple in its construction and machining thereof and prevents the twisting and bending of the swash plate.
An object of the present invention is, therefore, to provide a variable capacity swash plate type compressor which is free of the above-mentioned problems.
Another object of the present invention is to provide a variable capacity swash plate type compressor provided with a novel hinge mechanism which can be easily and inexpensively manufactured.
According to the present invention, there is provided a variable capacity swash plate type compressor comprising:
a housing means having a cylinder block with a plurality of cylinder bores formed therein and enclosing therein a crank chamber, a suction chamber, and a discharge chamber;
a drive shaft rotatably supported by said housing means
a plurality of pistons reciprocatively disposed in each of said cylinder bores;
a rotor mounted on said drive shaft so as to rotate together with said drive shaft in said crank chamber;
a swash plate operatively connected to said rotor via a hinge means and slidably mounted on said drive shaft to thereby change an inclination angle thereof in response to changes of pressure in said crank chamber;
a motion conversion means disposed between said swash plate and said pistons for converting rotation of said swash plate into reciprocation of said pistons in the respective cylinder bores; and
a control valve means for changing a pressure level in said crank chamber;
said hinge means including a support arm protruding from said rotor toward said swash plate, an arm having one end extending from said swash plate, and a pin means supported by the other end of said arm; and
said support arm having a recess with a depth being able to receive a displacement due to change of the inclination angle of said swash plate from one end surface of said support arm, and said arm is movably coupled with said support arm by said pin means so that said pin means is slidable in said recess in compliance with the change of the inclination angle of said swash plate.
Other objects, features, and advantages of the present invention will be understood from the detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings.